<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<script type="text/javascript">
  //有回调函数，就一定是异步的吗？
  setTimeout(()=>{
    console.log('ok')
  },1000)
  console.log(1)
  
  /*let arr = [1,3,5,7,9]
  arr.forEach((item,index)=>{
      console.log(`索引为:${index},该项为:${item}`)
  })
  console.log(1)*/
</script>

</body>
</html>